“Investigators have been summoned for emergency talks on the investigation in Salisbury, where the repercussions of a suspected nerve agent attack continue to grow.

The home secretary, Amber Rudd, will chair a meeting of the government’s Cobra committee at 3pm on Saturday to receive updates on the police inquiry, Downing Street said.

The Russian double agent Sergei Skripal, 66, and his daughter Yulia, 33, remain in critical condition in hospital after being exposed to a toxic substance in the Wiltshire city last Sunday.

DS Nick Bailey, who was part of the initial response by authorities, is also in a serious condition.

Part of the media scene in Salisbury this week. Photos by James Porteous

Almost 200 members of the armed forces arrived on the streets of Salisbury on Friday to support police investigating the nerve agent attack on the Skripals.

A Ministry of Defence spokesman said armed forces personnel would return to Salisbury in similar numbers on Saturday as the investigation and cleanup operation continued.

On Friday attention focused on the cemetery, with experts in hazmat suits setting up tents over the grave of Skripal’s wife, Liudmila, and the memorial to his son Alexander, who both died in recent years.

Soldiers, bomb disposal specialists, marines and RAF personnel were called in to help secure vehicles and scenes that may have been contaminated and to take the pressure off the police. The deployment included experts in chemical warfare.

The Metropolitan police dismissed reports that an exhumation took place on Friday and said there were no plans to carry one out.

Liudmila’s death certificate said she died of cancer in 2012, aged 59, while Alexander died in March last year in St Petersburg, aged 43, in unknown circumstances. He was cremated. Most attention seemed to be being paid to the site of his memorial stone, which is topped by a model of a St Bernard dog.

Earlier, a convoy of military lorries accompanied by police escorts, incident response units and an ambulance arrived at Salisbury district hospital to remove a police car believed to have been used in the response to the attack.

It has emerged that DS Bailey visited the Salisbury home of Skripal after he and Yulia were found slumped on a bench in the city centre. Investigators want to know if he was contaminated during that visit, or whether he visited the scene where they were found and was poisoned there or by items there. Sources say that it is believed to be more likely that Bailey became contaminated at the home.

The Metropolitan police commissioner, Cressida Dick, paid tribute to Bailey, his colleagues and other emergency services. She said: “It’s a very challenging investigation. It’s obviously a very challenging environment to work in.

And I guess these very vivid images that people are seeing just reminds people of what our first responders, what our forensics people, what our investigators do and may find themselves doing, and the professionalism and courage that takes.”

Dick declined to comment when asked about the former Met commissioner Lord Blair backing calls for 14 other deaths to be re-examined after the Salisbury incident.

At Saturday’s Cobra meeting cabinet ministers including the foreign secretary, Boris Johnson, and the defence secretary, Gavin Williamson, will be updated on the police investigation, which government sources described as “moving quite quickly”.

However, Downing Street stressed that the committee, which coordinates the government’s handling of emergencies, was not the forum for considering potential diplomatic responses.

With suspicion falling on the Russian state, Theresa May’s government is understood to haveseveral options for responding to the attack Mays said to be determined to be tougher than the UK was after the poisoning of Alexander Litvinenko in 2006.

Options include expelling diplomats, revision of sanctions, not officially sending a minister to the football World Cup, designating Russia as a state sponsor of terror – and even, though this is believed to be unlikely, declassifying intelligence implicating Vladimir Putin.

The thinking in Westminster is understood to be that the UK has few benefits from good relations with Putin and Johnson’s visit to Moscow was not deemed a success.

The Salisbury MP, John Glen, said constituents were demanding “decisive action” be taken against whoever is responsible. Glen, who is economic secretary to the Treasury, said: “A whole range of tools are at our disposal depending on who has perpetrated this act, including a number of financial and economic levers.”

Glen said he suspected the shock of what had happened would give way to “genuine anger at the audacity of what has taken place within our city”. But the government would not be “acting precipitously”, he said.

“Now is the time for cool heads and a rational examination of the facts. Once these are established, then, and only then, will an appropriate and proportionate course of action be taken.”

During a visit to Salisbury, Rudd described the attack as “outrageous”.

She said: “I understand people’s curiosity about all those questions, wanting to have answers, and there will be a time to have those answers. But the best way to get to them is to make sure we give the police the space they need to really go through the area carefully, to do their investigation and to make sure that they have all the support that they need in order to get that.”

Rudd added: “In terms of further options, that will have to wait until we’re absolutely clear what the consequences could be and what the actual source of this nerve agent has been.”

Among the troops in Salisbury were experts in surveillance from the Royal Tank Regiment, Royal Marines from 40 Commando and members of the RAF Regiment.

Chemical warfare instructors were on the ground as well as bomb disposal experts from 29 Explosive Ordnance Disposal and Search Group.

The use of a nerve toxin is seen as a key indicator of possible Kremlin involvement, with such substances usually held only in state military stockpiles.

Moscow has repeatedly denied it had anything to do with the attack, the same line used when Litvinenko was poisoned with radioactive polonium-210 in his cup of tea. A public inquiry a decade later concluded that the Kremlin had ordered the killing.

Meanwhile, the Russian embassy tweeted: “Investigation of Sergei Skripal case follows the Litvinenko script: most info to be classified, Russia to get no access to investigation files and no opportunity to assess its credibility.”